The present invention relates generally to pile drivers and more particularly to a pile driver of the drop hammer variety. More specifically, the present invention relates to such a drop hammer assembly which is crane supportable and nearly self-contained.
Pile drivers or pile hammers now in general use are frequently powered by means of compressed air, steam or diesel fuel within a self-contained cylinder. The hammers powered by steam or compressed air cylinders require auxiliary power sources such as air compressors and steam boilers which are costly additions to the pile driving rig and require considerable maintenance, fuel and in some cases, additional personnel.
Drop hammers are in less general use and derive their impact energy solely by hoisting a weight and then permitting it to fall freely under the influence of gravity to impact the pile being driven. Drop hammers are quite noisy and this noise problem has caused their use to be prohibited in some areas. The other hammer types discussed above also create considerable noise and in the case of air operated hammers, compressor noise, unless suppressed or muffled at great expense, exceeds permissible noise levels. Both the air and steam powered hammers cause pollutents from their respective power sources to be added to the atmosphere. Also, in cold weather operations, compressors are frequently difficult to start and boiler water supplies may freeze. Except for drop hammers, the manufacture of these powered hammers is costly, breakdowns are frequent due to the complexity of the designs and the repairs are time consuming and costly with spare parts often not readily available.
There has also been some investigation into the design and operation of hydraulically powered pile hammers utilizing hydraulic pistons or cylinders in lieu of the air, steam or diesel cylinder configurations discussed earlier. It has been found that due PG,3 to the extremely high pressures needed in these hammers, their manufacture is extremely expensive and more complex than their predecessors. In some cases, the high pressures generated by the hydraulic system constitute a safety hazard and the failure of the hammer cylinder to resist such pressures could result in rapid disintegration of the hammer with explosive force. Rupturing of the hydraulic lines or their overheating is also an inherent problem with such hydraulically powered hammers.
It would be highly desirable to retain the advantages of hydraulic systems while obviating the above-mentioned as well as other disadvantages.